Calculator



Nov. 9, 1943. A. L. THURsToN ET AL 2,334,135

CALCULATOR Filed DSC. 10, 1941 J; Jg 2f TRL/f Ala Q INVENTOR5 NEY Patented Nov. 9, 1943l CALCULATOR Arthur L. Thurston, Wantagh,` and Beauregard Sweeney, Great Neck, N. Y., assignors to Cox & Stevens Aircraft Corporation; a corporation of New York Application December 10, 13941, -Serial, No. 422,376

` 1 claim. (C1. 433`75 Our invention relates to calculating devices for use in solving problems encountered in aerial navigation, and is a continuing development of that type or form of calculator disclosed in a certain co-pending application Serial No. 388,139, led April 11, 1941, now Patent #2,296,692, Sept. 22, 1942, in the name of Arthur L. Thurston.

In aerial navigation, the magnetic compass is used almost exclusively as a means of determining direction and therefore, in the great majority of cases, it is the magnetic heading rather than the true heading that is either known or to be determined. With the calculator disclosed in said co-pending application, in order to take into account the magnetic variation, it is necessary either to set or to read the compass rose scale in conjunction with theproper divisionon the variation scale, rather than with the index arrow, or to convert the data and results of computations from magnetic to true by addition or subtraction of the variation angle. Either procedure is a potential source of error.

The object of the present invention is to provide an adjustable index which may be so set as to introduce automatically the required correction for a given magnetic variation when this index is used directly in cooperation with the scale on the compass rose.

With the above and other objects in view, the invention consists in the construction, combination and arrangement of parts hereinafter more iully described with reference to the accompanying drawing in which like characters denote like or corresponding parts in the Several views.

In the drawing:

Fig. 1 is a top plan view of a calculator generally similar to that disclosed in said co-pending application, but with the improvements made the subject of the present invention added.

Fig. 2 is a bottom plan view-of the calculator disclosed in Fig. 1, and c Figs. 3 and 4 are enlarged sectional views taken respectively on the dotted lines 3--3 and 4-4 of Fig. 1.

As stated above, the calculator as a whole is generally similar to that described and claimed in said co-pending application Serial No. 388,139. It includes a base member l; a slide member II movable in a slot I2 in the' base member and carrying a rotatable arm I3; a compass rose disc I4; and a true track index disc I5. The latter disc I5 and the arm I3 are connected by a mechanism I6 which imparts to the disc rotation in the same magnitude and sense as that imparted to the arm. A heading and tracklock l1 selectively holds the compass rose disc I4 stationary on the base I or permits it (the compass rose) to move as a unit with the disc I5". The detail construction of these members I0 to I1, inclusive, and the various scales and indices inscribed thereon are similar to the corresponding details disclosed in said co-pending application, and the method of operation thereof is as therein set forth.

Instead of the true heading index and the magnetic variation scale shown in my earlier application, the improved calculator comprising the present invention includes an adjustable heading index, the details of which and the method ci operation of which will now be disclosed.

Two slots I8 and I3 are provided in the base member i. a running t in the slot I8 (which is straight) for endwise movement along its length. A knob 2|, by which the slide is moved, has a reduced portion 22 which extends through the slide and serves as a pivot for one end of a link 23. The other end of the link 23 is pivotally connected to one arm 2t of a bell-crank 25 rotatably carried by a member 26 whoseaxis of rotation is coincident with that of the rotatable discs I4 and I5.

The other arm 2l of the bell-crank 25 is oiset as at 28 so as to extend from beneath the base member I up through the slot I9 (which is arcuate), with the extremity 29 of the arm 2l lying above the base member adjacent to the periphery of the compass rose disc Iii. An index 30, labelled Magnetic heading is inscribed on the arm extremity 29 so as to read on the scale 3l of the compass rose disc I4. v

- Referring back to the slide member 20, it will be noted that said member has inscribed thereon an index 32, opposite which, on the base member IIJ, there is provided a. scale 33 labelled Variation. The graduations on this scale 33 extend in either direction from a zero mark which is so located on the scale that when the index 32 is'moved opposite it the magnetic heading index 30 will lie on a line joining the centers of rotation of the arm I3 and the discs I4 and I5. Each graduation of scale 33 to the right (west variation) or left (east variation) of the zero mark'is located so that when the index 32 is moved opposite it, the index 30 will be moved to a, position above or below (respectively) the line joining the centers of rotation of the arm A slide member 20 is mounted with I3 and the discs I4 and l5 by the angle marked on the graduation.

Having described the construction of the calculator of the present invention it now remains to describe its method of operation. Briefly, the

The procedure thereafter is the same as that.y set forth in my co-pending application except' that the magnetic heading on the compass Aroseg,

scale 3| is set opposite the index 30-or if the de-` sired magnetic heading is to be determlnedit is read on scale 33 opposite the indexg32..

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in theart, after unout departing from the spirit or scope thereof. We aim in the appended claim to cover al1 such modications and changes.

We claim as our invention:

In a calculator, a base member provided with a fixed magnetic variation scale and with a rotatable `compass rose, amember carried by the base member and slidablv adjustable with respect to it, said slide member being provided with an index adapted for cooperation with said scale, a rotatable member provided with an index adapted for cooperation with said compass rose, .and a connection between said slide member and c said rfltatablel member for automatically shiftderstanding our invention, that various ,changeset ingthe position of the rotatable-member-index accordingly as the position of the slide-memberindex is shifted with respect to the magnetic variation scalei- I Y ARTHUR L. THURSTON.

BEAUREGARD SWEENEY. 

